What types of filters are categorized under high pressure?

High-pressure filters are designed to operate at elevated pressures to effectively separate contaminants and purify fluids. Reverse osmosis and nano filters fit this description as they typically require high pressure to achieve the necessary force for water to pass through these semi-permeable membranes. In reverse osmosis, water is forced through a membrane that allows only certain molecules and ions to pass, effectively removing a wide range of contaminants and resulting in purified water. Nano filtration operates similarly but targets slightly larger particles and divalent ions.

The other types of filters listed, like micro and ultra filters, while also capable of filtration, typically function at lower pressures compared to reverse osmosis systems. Sand and gravel filters mainly rely on gravity and do not operate under high pressure, and activated carbon and ceramic filters are generally designed for lower flow rates and operate efficiently without requiring high-pressure conditions. Thus, reverse osmosis and nano filters are the appropriate choices categorized under high pressure due to their operational requirements and effectiveness in purification processes.